22.4.6.2 Embedded Breakpoints

Since all breakpoints in a definition are cleared each time you reinstrument it, you might rather create an embedded breakpoint which is simply a call to the function edebug. You can, of course, make such a call conditional. For example, in the fac function, insert the first line as shown below to stop when the argument reaches zero:

(defun fac (n)
  (if (= n 0) (edebug))
  (if (< 0 n)
      (* n (fac (1- n)))
    1))

When the fac definition is instrumented and the function is called, Edebug will stop before the call to edebug. Depending on the execution mode, Edebug will stop or pause.

However, if no instrumented code is being executed, calling edebug will instead invoke debug. Calling debug will always invoke the standard backtrace debugger.